Pump or motor



July 2, 1940. E. ROSE ET AL 2,206,305

PUMP 0R MOTOR Filed April 28. 193'! INVENTOR ED L Ross (3 srmrv E.GROSSER ATTORNEY Patented July 2, 19 40 UNITED STATES 2,206,305 PUMP onoron Edwin L. Rose, Watertown, and Christian E. Grosser, Waterbury,Conn., assign'ors to The Waterbury Tool Company, Waterbury, Comm, acorporation of Connecticut Application April 28, 1937, Serial No.139,414 10 Claims. (Cl. 103-162 This invention relates to powertransmissions and more particularly tothose of the-type comprising twoor more fluid pressure energy translating devices, one of which mayfunction as a pumpand another as a fluid motor. The invention isparticularly concerned with the positive displacement type offluidpressure energy translating device wherein a plurality of pistons andcylinders are provided and in which a rotary plate valve is used foralternately connecting each cylinder to the inlet and outlet port inphase with the piston strokes. A common type of device i of this classutilizesa rotary cylinder barrel having cylinders parallel to the axisthereof and spaced on a circle about that axis together with a swashplate mechanism for causing reciprocation of the pistons as the barrelrevolves. One end face of the cylinder barrel is provided with a flatsurface through which cylinder ports extend to each cylinder, itssurface running against a flat surface on a stationary valve plate whichis provided with a pair of arcuate inlet and out-' let ports with whichthe cylinder ports alternately communicate in theircycle'of rotation.

It is necessary in devices of this character to maintain the cylinderbarrel in close proximity to the valve plate so as to minimize leakageatthis point. It has been customary to maintain this small runningclearance between the cylinder barrel and valve port by establishing ahydraulic force of predetermined ratio to the operating pressure whichconstantly urges the cylinder bar- ,rel against the valve plate. Thishas been accomplished by careful correlation between the 35 area of thesurface of contact between the cylinder barrel and valve plate, the areaof the cylinder and valve plate ports, and the cylinder areas. For thispurpose the cylinder ports aremade a small fraction of the cylinder areaso that a sub- I 40 stantial area at the end of the cylinder bore isexposed to fluid pressure tending to urge the barreltoward the valveplate.

In designing machines of this character it is desirable from certainstandpoints to decrease the 4.5 ratio between the cylinder diameter andthe diameter of the circle upon which the cylinders are spaced. Thus fora given overall size of the unit, a smaller piston area permitsthemaximum operating pressure to be increased without in- 50 creasingthe bearing loads at the swash plate mechanism. Such a procedurepresents one difflculty, however, in that in order to maintain f thesame hydraulic balance ratio between the' cylinder barrel and valveplate, the contact sur- 55 face must be decreased to a point where theleakage ratio becomes excessive; that is, the contact surface boundingthe two arcuate valve ports becomes so narrow radially in relation toits circumferential length that even though the same clearance bemaintained, the leakage is propor- 5 tionally much higher. Accordingly,it is found that in the design of devices of the construction heretoforeused, a definite limit of operating pressure is reached which cannot beexceeded without either overloading the bearings in the swash platemechanism or permitting excessive leakage at the valve plate contactsurfaces.

It is, accordingly, an object of the present invention to provide afluid pressure energy translating device having a plate type of valvemechanism wherein means are provided for permitting operation at higherpressures than have been possible heretofore without either overloadingthe bearings or permitting excessive leakage in the valve mechanism.

A further object is to provide a cylinder barrel construction fordevices of this class wherein the portion containing the cylinder portsand cooperating with the valve plate is movable indegendently of theportion containing the cylinder ores.

A further object is to provide a fluid pressure energy translatingdevice of the character described and to provide a. cylinder barrelconstruction therefor wherein that portion of the cylin- 0 der barrelcooperating with the valve plate may be hydraulically balanced and maybe designed to provide any hydraulic balance desired independently ofthe cylinder areas.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing wherein a preferred form of the present invention is clearlyshown.

In the drawing: 40 Fig. 1 is a longitudinal crosssection of a fluidpressure energy translating device incorporating a preferred form of thepresent invention.

Fig. 2 is a cross section on line 2-2 of Fig. 1. Fig. 3 is a crosssection on line 3-3 of Fig. 1. The device illustrated in the drawingrepresents a fluid pressure energy translating device of the samegeneral type as the well-known Waterbury device and may be operatedeither as a pump or as a fluid motor. The mechanism illustrated is ofthe variable displacement type although it will be understood that theinvention may be incorporated to equal advantage in devices having aflxed displacement. The device comprises a casing in having its openleft-hand end closed by a valve plate l2. Journalled on bearings I4 and16 in the casing and valve plate, respectively, is a main shaft it. Theright-hand end of the shaft carries a composite cylinder barrelgenerally designated at 20, the barrel being so fastened to the shaft|8.as to rotate therewith. A socket ring 22 is journalled in a tiltingbox 24 on radial and thrust bearings, not shown, and is connected to theshaft through the medium of a suitable universal joint, not shown, sothat the socket ring 22 may be caused to rotate with the shaft 3 eventhough the plane of rotation of the socket ring be inclined in eitherdirection away from the perpendicular position shown .in the drawing.The inclination of the plane of rotation of the socket ring 22 may bevaried by adjusting the tilting box 24 on its trunnions 26 by means of acontrol shaft 28 which is connected by suitable linkage, not shown, tothe tilting box 24. With the exception of the detailed construction ofthe cylinder barrel 20 the mechanism thus far described is well knownand per se forms no part of the present invention.

The cylinder barrel 20 comprises a plate 30' which is shown as beingkeyed to the shaft H8. The plate 30, however, may be journalledseparately on bearings at its circumference located on the casing, ifdesired. Positioned in recesses 32 in the plate 30 are a plurality ofsleeves 34 having slight radial clearance in the recesses for permittingthe sleeves to properly align themselves with the other parts of thecylinder barrel about to be described. The sleeves 34 are provided withinterior bores 36 within which pistons 38 are reciprocable and arearticulated by connecting rods 40 to the socket ring 22. At the lefthandend of the sleeves 34 there is provided a plate-like member 42 having aplurality of cylindrlcal chambers 44 within one of which each of thesleeves 34 is telescoped. The member 42 is slid ably but not rotatablyattached to the shaft l8. The member 42 has a flat surface which abutsthe flat surface of the valve plate i2. Extending through the member 42at each chamber is a cylindrical port 46 of substantially smaller areathan the area of the cylindrical chambers 44. The'contact surface of thevalve plate l2 appears in Fig. 2 from which it will be seen that anannular band 48 is provided and contained within this band are a pair ofarcuate valve ports 50 which communicate with the supply and deliveryconduits 52. Auxiliary contact pads 54 and 56 may be provided foradditional bearing surface which is independent of the operatingpressure as described in the patent to Durner 1,867,308.

The present invention may be utilized to greatest advantage in machine'swherein it is desired to use relatively small diameter pistons on alarge diameter cylinder circle. Thus, if the radius B of the piston isless than four tenths the chord A connecting two adjacent cylindercenters, the conventional construction involves difliculty with theleakage ratio at the valve plate pressure surface. Under theseconditions the annular pressure surface 48, which would exactly balancethe fluid pressure forces on a conventional one piece cylinder barrel,becomes so narrow radially that the leakage or slip is excessive. By theprovision of the two part cylinder barrel, the cylindrical chambers 44may be made with a radius C greater than four tenths of the chord A, andthus the member 42 may be proportioned as desired to balance with asufliciently wide pressure surface 48. The factor, four tenths of thechord A to .which the. radii are compared is not a critical ,46, and theports 46 and 50.

value in the usual sense of the term, but may be considered arepresentative of present day practice, in that the average machine ifprovided with a piston radius B less than this value, will have what isconsidered to be excessive leakage for most purposes if a conventionalone piece cylinder barrel is utilized. Obviously some pump ortransmission applications may require even less permissible leakage ormay permit of greaterleakage without disadvantage. In the former case itmay be desirable to make use of the present invention even though thepiston radius be somewhat greater than four tenths the chord A. In thelatter case the conventional construction may be satisfactory with thepiston radius somewhat less than this value.

In operation as a pump, the shaft I8 may be driven by any suitable primemover causing the cylinder barrel 20 and socket ring 22 torevolvetherewith. So long as the tilting box 24 is held in the perpendicular orneutral position illustrated, no fluid will be pumped through the devicesince the pistons will not partake of any reciprocating motion in thecylinders 36. If the tilting box be inclined from the positionillustrated, the pistons will be caused to reciprocate in the cylinders36 to an extent determined by the angle of inclination of the tiltingbox 24. As each cylinder port 46 passes on to one of the valve plateports 60, the corresponding piston will begin an outward stroke drawingfluid into the cylinder 36 and chamber 44. Substantially 180 later thesame port 46 passes on to the other valve port 50 and the piston beginsan inward stroke discharging fluid into the second valve port 56 Thequantity of fluid pumped is thus dependent on the angle of inclinationof the tilting box 24.

Likewise if the tilting box beinclined on the op-" exerted in theannular areas at the left ends of the sleeves 34 is transmitted throughthe plate 36 and shaft l8 to the bearings l4. The member 42 is subjectat any given operating pressure to the resultant of the unit pressureapplied over the areas'of the chambers 44, the annular band Since thearea of the chambers 44 is independent of the area of the cylinders 36,-the former and the ports 46 and 56 and the contact pressure surface 48may be proportioned to provide any desired radial width of the band 48on each side of the ports 50. Thus, the leakage ratio at the valvemechanism may be kept down to a reasonable value while the diameter ofthe cylinders 36 and the pistons 38 may be made as small as desiredwithrespect to the diameter of the circle on which the cylinders arelocated. Thus, the loadings on the thrust bearings in the socket ring 22and the hearings in the universal joint may be kept within safe valuesat higher operating pressure because of the smaller piston area withoutreducing the leakage ratio of the valve plate.

While the form of embodiment of the invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. In a fluid pressure energy translating device flO the combination ofa cylinder barrel having a plurality of parallel cylinders formedtherein, a piston reciprocable in each cylinder, swash plate mechanismfor causing reciprocating motion of the pistons, and a valve platecooperating with one end of said cylinder barrel to control the entryand egress of fluid to and from said cylinders, said cylinder barrelbeing formed in two relatively movable sections each having a series oftelescoping portions communicating with each cylinder, said telescopingsections providing at each cylinder an expansible chamber having an areagreater than the piston area whereby fluid pressure forces are set uptending to separate the two sections of the cylinder barrel and maintainone section pressed against the valve plate with a net force greaterthan that due to the thrust of the pistons alone.

2. In a fluid pressure energy translating device the combination of acylinder barrel having a plurality of parallel cylinders disposed inspaced relation about the barrel axis, said cylinders having an internalradius not greater than four tenths of the chord of the cylinder circleextending between adjacent cylinder centers, a piston reciprocable ineach cylinder, motion converting means for causing reciprocating motionof the pistons, a valve plate cooperating with an end portion of thecylinder barrel for controlling the entry and egress of fluid to andfrom said cylinders, a movable end plate abutting the valve plate andslidably engaging said cylinders to form expansible chambers at the endof each cylinder, said chambers having a radius greater than four tenthsof the chord of the cylinder circle extending between adjacent cylindercenters.

3. In a fluid pressure energy translating device i the combination of acylinder barrel having a plurality of cylinders disposed in spacedrelation about the barrel axis, a pistonreciprocablein each cylinder,motion converting means for causinglreciprocating motion of the pistons,a valve plate cooperating with an end portion of the cylinder barrel forcontrolling the entry and egress of fluid to and from said cylinders, amovable end plate abutting the valve plate and slidably engaging saidcylinders to form expansible chambers at the end of each cylinder, saidchambers having a diameter substantially differing from the cylinderdiameter, and means for limiting movement of said cylinders out of saidchambers.

4. In a fluid pressure energy translating device the combination of amember having a plurality of parallel cylindrical chambers formedtherein and disposed in spaced relation substantially on a circle, avalve plate cooperating with one end of said member to control the flowof fluid to and from said chambers, a plurality of sleeves slidablyengaging the cylindrical walls of said chambers, pistons reciprocable insaid sleeves, motion converting means for causing reciprocation of saidpistons upon relative rotation between said member and valve plate, andmeans associated with said member for, holding said sleeves againstendwise movement independently of endwise movement of said member.

5. In a fluid pressure energy translating device the combination of amember having a plurality of parallel cylindrical chambers formedtherein and disposed in spaced relation substantially on a circle, avalve plate cooperating with one end plate mechanism for causingreciprocation of said pistons upon relative rotation between said memberand valve plate, and means associated with said member for holding saidsleeves against endwise movement independently of endwise movement ofsaid member.

6. In a. fluid pressure energy translating device the combination of amember having a plurality of parallel cylindrical chambers formedtherein and disposed in spaced relation substantially on a circle, avalve plate cooperating with one end of said member to control the flowof fluid to and from said chamberaa plurality of sleeves slidablyengaging the cylindrical walls of said chambers, pistons reciprocable insaid sleeves, motion converting means for causing reciprocation of saidpistons upon relative rotation between said member and valve plate, andmeans non-rotatably associated with said member for holding said sleevesagainst endwise movement independently of endwise movement of saidmember, said sleeves engaging said last named means in a mannerpermitting slight misalignment between said chambers and said last namedmeans.

7. A cylindrical barrel for a fluid pressure energy translating devicecomprising a plurality of sleeves having an interior bore and acylindrical exterior surface, a member at one end of said sleeves forpositioning said sleeves against endwise movement, a member at the otherend of said sleeves having chambers telescopically engaged withandfreely slidable on the sleeves during operation of the device andhaving ports extending through the member and communicating with saidchambers.

8. A cylinder barrel fora fluid pressure energy translating devicecomprising means forming a plurality of cylinders adapted to be closedat one end by pistons receivable in the cylinders, a movable end memberslidably engaging said cylinders to form expansible chambers at the endof each cylinder, said chambers having a diameter substantiallydiffering from the cylinder diameter, and means forlimiting movement ofsaid cylinders out of said chambers.

9. A cylinder barrel for a fluid pressure energy translating devicecomprising a plurality of sleeves having an interior bore and acylindrical exterior surface, a member at one endof said sleeves forpositioning said sleeves against endwise movement, 9. member at theother end of said sleeves having chambers telescopically engaged withand freely slidable on the sleeves during operation of the device andhaving ports extending through the member and communicating with saidchambers, said last member having a flat face surrounding said ports attheir ends opposite from said chambers.

10. A cylinder barrel for a fluid pressure energy translatingdevicecomprising means forming a plurality of cylinders adapted to beclosed at one end by pistons receivable in the cylinders, a movable endmember slidably engaging said cylinders to form expansible chambers atthe end of each cylinder, said chambers having a diameter substantiallydiffering from the cylinder diameter, and means for limiting movement ofsaid cylinders out of said chambers, said member having ports extendingthrough the member and communicating with said chambers, and having aflat face surrounding said ports at their ends opposite from saidchambers.

EDWIN L. ROSE. CHRISTIAN GROSSER.

